1. Field of the Invention
This invention concerns polymeric films and more particularly polypropylene films having good gloss.
2. Description of Related Art
It has been proposed hitherto in EP0004633-A to produce opaque polypropylene films, the opacity resulting from microvoids within a core layer of a three layer film structure. The outer heat sealable layers of these films impart a degree of gloss to the films. However, higher degrees of opacity combined with high gloss values have been sought in the art.
One proposal for increasing the opacity of polypropylene films has been to use titanium dioxide as a filler. GB2195947-A, for example, describes biaxially oriented polypropylene films having a base layer of a voided propylene homopolymer with an outer heat sealable polymeric layer containing titanium dioxide thereon. The titanium dioxide in the outer layer imparts improved opacity to the films compared with analogous voided films such as are described in EP 0004633-A, but the surface gloss of the films is reduced.
It has been proposed in EP 0517109-A to use a layer of a propylene homopolymer containing finely divided titanium dioxide between a propylene homopolymer core layer and a polymeric outer layer containing no filler, and such films are said to have high gloss.